American Horse Fly

Description: 3/4-1 1/8" (20-28 mm). Large, broad. Head tan to ash-gray between large green eyes and on rear surface. Antennae reddish brown. Thorax brownish to blackish with gray hair. Abdomen is blackish red-brown with short gray hair across rear margin. Hind tibiae do not have spurs. Wings smoky; brown to black near base.

Warning When the female bites, the wound inflicted often continues to bleed for several minutes because the fly's saliva contains an anticoagulant that prevents clotting. A single animal may suffer a debilitating loss of blood if many of these insects attack it.

Food Male eats pollen and nectar; female takes blood of large mammals. Larva preys on aquatic insects and other small animals.

Life Cycle Eggs masses are attached to plants overhanging fresh water, into which larvae drop. Larvae over winter in muddy bottom 2 winters, they pupate in spring. Males are short-lived, but females may survive until fall.

Habitat Near swamps, marshes, and ponds.

Range Newfoundland to Florida, west to Texas and northern Mexico, north to Canadian Northwest Territories.